Persistence for data structures other than key-value store

[dpk]

See this IRC conversation from 2017: https://freenode.logbot.info/whatwg/20171129#c1373257

Essentially, at the moment it’s very inconvenient to try to persist large data structures that don’t fit the key/value store model of IDB/localStorage. If I want a trie or a suffix array to persist, for example, there’s no really good way to do that. In 2017, I suggested adding a way to create a persistent, mmap’d array buffer, and there seemed to be interest in that from the few people who participated in the conversation, but that’s just one option.